Influence of Film Thickness on Intrinsic Growth Stress and Raman Evaluation of Tetrahedral Amorphous Carbon Films

Abstract

To investigate the effects of film thickness on Raman characterization and intrinsic stress of tetrahedral amorphous carbon and ascertain the correlations between stress and Raman spectra, the ta-C films with different film thickness were deposited on the polished P-type (100) c-silicon substrate with the same conditions by the filtered cathodic vacuum arc technology. The film thickness was measured by the surface profiler and the atomic force microscope; stress was calculated according to the curvature of the stress samples examined by the surface profiler; the microstructure of the films was characterized by the Ramanscope. It has been shown that the stress drops down continuously and the dropping rate turns mild with the increase of film thickness. When the film thickness surpasses 30 nm, the compressive stress is kept at less than 5 GPa. The intensity of the first and second order peak of the c-Si substrate in the visible Raman spectra gradually depresses with the increase of thickness. However, the FWHM is minimal and the maximal intensity is highest from 50 nm to 80 nm, accordingly the clearest Raman signals can be acquired in this scale. Additionally, the position of the asymmetric broad peak gradually shifts towards the lower wavenumber with the increase of thickness and the decease of intrinsic stress.